High resolution laser Thomson scattering system with automatic data analysis software platform for diagnosis of the low-temperature plasmas.

Abstract

Accurate measurements of electron temperature (Te) and electron density (ne) are important for understanding the properties of plasma, especially for the low-temperature plasma dominated by the free electrons. In this work, a high resolution laser Thomson scattering (LTS) diagnosis system with a software platform for processing data is established to accurately measure the Te and ne in low-temperature plasmas. In this system, a homemade Triple Grating Spectrometer (TGS) is elaborated to suppress the intense stray light and Rayleigh scattering light. The TGS with high etendue (with an f-number of f/3.3) and high spectral resolution (0.07nm in full-width-half-maximum at 532nm) allows the LTS system to measure the plasma with the ne and Te as low as 1.0 × 1017m-3 and 0.1eV, respectively. Besides the development of the experimental setup, a software platform is specially designed to automatically process the complicated LTS spectra to determine ne and Te in real time during the acquirement of data. The error analyses indicate that the uncertainty of ne is around 12% and the uncertainty of Te is about 10% when Te > 0.2eV. Using the LTS system, we have successfully measured ne and Te in the cascaded arc plasma, nanosecond pulse discharge plasma, and inductively coupled plasma. The results demonstrate that the LTS system has significant potential for the diagnosis of various low temperature plasmas.